In the French capital, he met with the Slovene literary critic Josip Vidmar, who introduced him to the story of Hassan-i Sabbah.

A further stimulation for the novel came from the assassination of Alexander I of Yugoslavia perpetrated by Croatian and Bulgarian radical nationalists, on the alleged commission of the Italian fascist government.

The novel is set in the 11th century at the fortress of Alamut, which was seized by the leader of the Ismailis, Hassan-i Sabbah or Sayyiduna (سیدنا, "Our Master").

The story commences with the journey of young ibn Tahir, who is, according to his family's wish, intending to join the Alamut garrison.

Hassan managed to achieve such level of obedience by deceiving his soldiers; he gave them drugs (hashish) to numb them and afterwards ordered that they be carried into the gardens behind the fortress—which were made into a simulacrum of heaven, including houris.

After the siege, Hassan orders ibn Tahir to go and kill the grand vizier of the Seljuk sultan Nizam al-Mulk.

When ibn Tahir returns, Hassan receives him and also reveals him his true motto: "Nothing is an absolute reality, all is permitted".

Some of the contemporaneous literary critics, such as Lino Legiša, have interpreted it as an allegory of the TIGR, an organization formed in order to fight the Fascist Italianization in the former Austrian Littoral.

[6] Earlier it was translated into about 18 other languages including Czech (1946),[7] Serbo-Croatian (1954), French (1988), Spanish (1989), Italian (1989), German (1992), Persian (1995), Arabic, Greek (2001), Korean and Slovak.